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Nirnn STATES ATENT FFICE.

MILO Cr. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELIJOGGS\VITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,368, dated. October26, 1897.

Application filed July 26, 1890. Serial No. 360,077. (No model.)

To rtZZ 1072,0722, it may concern.-

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cookand State of Illinois, temporarily residing at Stuttgart, in the Empireof Germany, have invented certain new and useful Improvements inMultiple Switchboards for Telephone-Exchanges, of which the following isa full, clear, concise, and exact description, reference being had tothe accompanying drawing, forming a part of this specification.

My invention relates to a metallic-circuit telephone-exchange system inwhich the lines are connected together for conversation by means ofpairs of loop-switch plugs, the two contact-pieces of one plug of a pairbeing connected to the two contact-pieces of the other plug by means ofdouble flexible conductors. Such a system is called a doublecord system.

My invention includes a system of testing and apparatus, circuits, andconnections whereby the operator may quickly and with few motionsconnect her telephone to the circuit of the calling-line, may ascertainby a test whether the line wanted is alreadyin use, may connect the twolines together, may send a signaling-current over the circuit of theline wanted, may connect her telephone to the circuit to determinewhether the subscribers are through conversation,and may disconnect thelines and place the apparatus in readiness for receiving new calls.

In the accompanying drawing, illustrating my invention, A A aresectional views of sections of two switchboards to which the same linesconnect. Each switchboard has a spring-jack or similar switch for eachline. Each switch has a contact-spring which is normallyin contact witha contact-point, but is separated from the point when a switchplug isinserted into the switch, and has a contact-piece which is insulatedfrom the other parts (except by the circuit connections) and which isconnected with a contactpiece of the switch-plug when the plug isinserted. This contact-piece is adapted to have a test plug or deviceapplied to it for testing.

The contact-sprin gs are shown at g g,whi1e h 715110 the contact-pointson which the springs normally bear, and j j are the contact-pieces ofthe switches.

Z Z are the switch-holes through the fronts of the rubber strips a Z),on which the metal parts of the switches are mounted.

The switch-plugs (marked D D) are loopplugs adapted to be inserted intothe switches, and when a plug is inserted into a switch it separates thepoints normally in contact and one of its contact-pieces formsconnection with the spring g, while the other forms connection with thecontact-piecej of the switch.

B is the test-battery, and \V W are lineannunciators.

Gin each case in the drawing is a ground connection.

Two lines and their switches on the boards and their annunciators areshown in the drawing. The circuits of the lines are as follows, and, asshown, one side or branch of the line passes successively through thepairs of contact-points g h of its switches on the boards, passing ineach case to the spring first and from the last contact-point hthroughthe line-annunciator to the common groundwire of the lines in which isthe test-battery B and through the battery to ground. The other side orbranch of the line is connected to contact-piecesjj of the switches ofthe line.

The line should be grounded at the subscribers station while thesubscribers telephone is not switched for use and this ground connectionopen while the telephone is thus switched. This can be accomplished intheusual way for such a connection by means of contact-points on thetelephone-switch. The signal-receiving bell should be placed in thisground-connection circuit.

For each pair of plugs there is an operators switching device. Thesedevices are marked '0 C. There are one pair of plugs and one switchingdevice shown at each board. Other pairs may be added as required andconnected to the operators special apparatus, substantially as will bedescribed.

d d are the rubber supports of the switching devices.

ff are a pair of contact-springs of a device.

l, 2, 3, and 4 are contact-points. dis a movable piece to one end ofwhich is attached the irregular rubber piece 19 u 'r' and shown at boardA, the two springs ff are in contact with 2 and 3, respectively, whenthe piece is moved to its central position, so that the springs rest onu, f is in contact with 1 and f is in contact with 3, and when the,

piece is moved to its inner position, as shown at A, f is in contactwith neither of the points and f is in contact with 4.

'u 'u are clearing-out annunciators, of which there is one for each pairof cords.

B B are calling generators or batteries.

is are two point-keys, and t t are'operators telephones, of which theremay be one of each kind of apparatus for each operator.

Theconnections of a pair of plugs to its operators switching device andto the operators special apparatus are as shown and as follows: The twocontact-pieces of one of the plugs are connected to the twocontact-pieces of the other plug, respectively, by two flexible-cordcircuits. One of these cord-circuits is connected to spring f and theother to spring f of the device of the pair. Contacts 2 and 3 areconnected together through the operators telephone. Contact 1 isconnected to the ground through the calling generator or battery and thepoints of the key is. Contact 4: is connected through the clearing-outannunciator to the cord-circuit which is connected to f. The wire whichconnects the two coils of the telephone is connected with the ground.

The commutator-piece of eachswitching device remains normally in itsouter position, as shown at board A.

The operation of the system is as follows: When the operator at anyboard observes the annunciato-r of a line to indicate a call, she placesone of the plugs of a pair of her plugs in the switch of the line. linedisconnected from its normal ground connection through the test-batteryand is included in circuit with the operators telephone. The-connectionis. from the two contact-pieces of the plug to the springs f f of theswitching device and thence to the two sides of the telephone throughcontacts 2 and 3, respectively. The operator then finds out byconversation what line is wanted. She then tests the line by placing acontact-piece of the other plug of the pair on the piece j of the switchof the line wanted, and, if she hears a By so doing thethen presses thecommutator-piece to its central position and the telephone isdisconnected from the circuit and .the circuit is grounded through thecalling-generator. This connection is made by the contact between fand 1. A calling-current will therefore go to the circuit of the linewanted and to ground through its normal ground connection through itssignal-receivin g bell and the bell will ring. The operator thenpressesthe commutator-piece to its lower position, as shown at A, and f is incontact with 4 and the other points of the device are open. Thegenerator is thereby disconnected from the circuit and the circuit isbridged or cross-connected through the clearing-out annunciator, and anyclearingout signal sent over the circuit of either line will beindicated on the annunciator.

Should the operator desire to listen to the circuit to determine whetherthe subscribers are through conversation, she opens the contact-pointsof the key and while the key is in that position moves thecommutator-piece to its outer position, when the circuit is bridged orcross-connected through the telephone. The operation of the key preventsany calling-current from going to the lines to give a false signal thatthey are wanted.

The operations of answering a call and making a connection are, first,to place a switchplug in the switch of the calling-line second, to testthe line wanted with the other plug; third, to place the plug in theswitch, and,

fourth, to press the commutator-piece from its upper to its lowerposition. The lines are thereby connected together and signalingcurrentsent to the line wanted and they are left with their circuit bridged bya clearing out annunciator.

To disconnect a connection, the operator merely takes the plugs from theswitches and moves the commutator-piece of the switching device to itsupper position.

When two subscribers lines are connected togetherintoa closed circuitfor conversation, as described, and the operator, by means of hercommutator-piece, sends a calling-cur- -rent from ground to one side ofthe closed telephone'circuit, the current passes over a circuitv toground at the station of the called subscriber, ringing his bells, andif the calling subscriber has hung up his telephone while Waiting forhis connection his bell is also rung by a portion of the calling-currentpassing through his grounded bell-circuit,

so that whenever two subscribers" telephones are upon their respectivehooks their lines are connected to ground through their switches andbells and the bells will be run-g by a current connected at centralbetween the line-circuit, and ground. It is evident that by connectingone contact of a pair of contacts to: the closed telephone-circuit andthe other contact through acall-generator to ground this result issecured.

I use the terms bridge and cross-connect in connection with a completemetallic circuit to describe a connection between one side or branch ofthe circuit and its other side or branch, and an instrument in a bridgeor erossconnecting circuit is not in the direct circuit, but is in acircuit connection across the two sides or branches of the circuit.

I claim as my invention and desire to secure by Letters Patent- 1.Inatelephone-exchange system, two metalliccircuit lines temporarilyconnected together into a closed metallic circuit for conversation, andan operators telephone temporarily in a bridge across the two sides ofsaid circuit, in combination with a calling-generator grounded on oneside, a switching device, two normally closed pairs of contacts in saidbridge, one on each side of the telephone, a pair of contacts normallyopen one of which contacts is connected to the other side of thegenerator and the other of which contacts is connected to said closedmetallic circuit, and a commutator-piece adapted to be in threepositions, in the first position said normally closed contacts beingclosed, in the second position, said normally closed contacts being openand the other pair closed and in the third position all of said pairs ofcontacts being open, substantially as set forth.

2. In a telephone-exchange system, two metallic-circuit linestemporarily connected together into metallic circuit for conversation,and an operators telephone temporarily in a bridge across the two sidesof said circuit, in combination with a calling-generator grounded on oneside, a switching device, two normally closed pairs of contacts in saidbridge, one on each side of the telephone, a pair of contacts normallyopen one of which is connected to the other side of the generator andthe other to said metallic circuit, a keyin circuit with said generator,having a pair of contacts normally closed but opened at the will of theoperator, and a commutator-piece adapted to be in three positions, inthe first position said normally closed contacts being closed, in thesecond position said normally closed contacts being open and the otherpair closed and in the third position all of said pairs of contactsbeing open, substantially as set forth.

3. In atelephoneexchange system, two metallic-circuit lines temporarilyconnected together into a closed metallic circuit for con- Versation andan annunciator temporarily in a bridge across the two sides of saidcircuit, in combination with a calling generator grounded on one side, aswitching device, two normally closed pairs of contacts in said bridge,one on each side of the annunciator, a pair of contacts normally open,one of which contacts is connected to the other side of the generator,and the other of which contacts is connected to said metallic circuit,and a commutator-piece adapted to be in two positions, in the firstposition said closed contacts being closed, in the second position saidclosed contacts being open, and the other pair closed, substantially asset forth.

4. In a telephone-exchange system, two metallic-circuit linestemporarily connected together into metallic circuit for conversation,and an annunciator temporarily in a bridge across the two sides of saidcircuit, in combination with a calling-generator grounded on one side, aswitching device, two normally closed pairs of contacts in said bridge,one on each side of the annunciator, a pair of contacts normally open,one of which is connected to the other side of the generator and theother to said metallic circuit, akey in circuit with said generator andhaving a pair of contacts normally closed but opened at the will of theoperator, and a commutator-piece adapted to be in two positions, in thefirst position said closed contacts being closed, in the second positionsaid closed contacts being open and the other pair closed, substantiallyas set forth.

5. In a telephone-exchange system, a pair of loop-switch plugs, the twocontact-pieces of each of which are respectively connected with the twocontact-pieces of the other, by two flexible switch-conductors, and anoperators telephone temporarily in a bridge across the two flexibleconductors, in combination with a calling-generator grounded on oneside, a switching device, two normally closed pairs of contacts in saidbridge, one on each side of the telephone, a pair of contacts normallyopen, one of which contacts is connected to the other side of thegenerator, and the other of which contacts is connected to one of saidconductors, and a commutator-piece adapted to be in three positions, inthe first position said normally closed contacts being closed, in thesecond position said normally closed contacts being open and the otherpair closed, and in the third position all of said pairs of contactsbeing open,substantially as set forth.

6. Ina telephoneexchange system, a pair of loop-switch plugs, the twocontact-pieces of each of which are respectively connected with the twocontact-pieces of the other by two flexible switch-conductors, and anoperators telephone temporarily in a bridge across the two flexibleconductors, in combination with a calling-generator grounded on oneside, a switching device, two normally closed pairs of contacts in saidbridge, one on each side of the telephone, a pair of contacts normallyopen, one of which is connected to the other side of the generator andthe other to one of said conductors, a key in circuit with saidgenerator and having a pair of contacts normally closed but opened atthe will of the operator, and a commutator piece adapted to be in threepositions, in the first position said normally closed contacts beingclosed, in the ICS of loop-switch plugs, the two contact-pieces side, aswitching device, two normally closed pairs of contacts in said bridge,one on each side of the telephone, a pair of contacts normally open, oneof which contacts is connected to the other side of the generator, andthe other of which contacts is connected to one of said conductors, anda commutator-piece adapted to be in two posit-ions, in the firstposition said closed contacts being closed,,in the second position saidclosed contacts being open, and the other pair closed, substantially asset forth.

8. In a telephone-exchange system, a pair of loop-switch plugs, the twocontact-pieces of each of which are respectively connected with the twocontact-pieces of the other by two flexible switch-conductors and anoperators telephone temporarily in a bridge across the two flexibleconductors, in combination with a calling-generator grounded on oneside, a switching device, two normally closed pairs of contacts in saidbridge, one on each side of the telephone, a pair of contacts normallyopen, one of which is connected to the other side of the generator andthe other to one of said conductors, a key in circuit with saidgenerator and having a pair of contacts normally closed but opened atthe will of the operator, and a commutator-piece adapted to be in twopositions, in the first position said closed contacts being closed, inthe second position said closed contacts being open and the other pairclosed, substantially as set forth.

9. In atelephone-exchange system, two metallic-circuit lines temporarilyconnected together in metallic circuit for conversation, and a bridgecircuit or connection across the two sides of said metallic circuit, incombination with an operators telephone, an annunciator, acalling-generator grounded on one side, a switching device containingpairs of contacts to connect at will either said telephone or saidannunciator into said bridgecircuit, and a pair of normally opencontacts adapted to be closed at the will of the opera tor, one of whichcontacts is connected with said metallic circuit and the other of whichcontacts is connected with the other side of the generator,substantially as set forth.

10. In a telephone-exchange system, two metallic-circuit linestemporarily connected together in metallic circuit for conversation, anda bridge circuit or connection across the two sides of .said metalliccircuit, in combination with an operators telephone, an annunciator, acalling-generator grounded on one side, a switching device containingpairs of contacts to connect at will either said telephone or saidannunciator into said bridgecircuit, a pair of normally open contactsadapted to be closed at the will of the operator, one of which isconnected with said metallic circuit and the other with the other sideof the generator, and a key in circuit with said generator, and having apair of contacts normally closed but opened at the will of the operator,substantially as set forth.

11. In a telephone-exchange system, a pair of loop-switch plugs, the twocontact-pieces of each of which are respectively connected with the twocontact-pieces of the other by flexible switch-conductors, and a bridgecircuit or connection across the two conductors, in combination with anoperators telephone,

an annunciator, a calling-generator ground-.

ed on one side, a switching device containing pairs of contacts toconnect at will either said telephone orsaid annunciator into saidbridge-circuit, and avpair of normally open contacts adapted to beclosed at the will of the operator, one of which contacts is connectedwith one of said switch-conductors, and the other of which contacts isconnected with the other side of the generator, substantially as setforth. v

12. In a telephone-exchange system a pair of loop-switch plugs, the twocontact-pieces of each of which are respectively connected with the twocontact-pieces of the other by flexible switch-conductors, and a bridgecircuit or connection across the two conductors, in combination with anoperators telephone, an annunciator, a calling-generator grounded on oneside, a switching device containing pairs of contacts to connect at willeither said telephone or said annunciator into said bridge-circuit, apair of normally open contacts adapted to be closed at the will of theoperator, one of which is connected with one of said conductors, and theother with the other side of the generator, and a key in circuit withsaid generator and having a pair of contacts normally closed but openedat the will of the operator, substantially as set forth.

13. In a telephone-exchange system, two metallic-circuit linestemporarily connected together in metallic circuit for conversation, incombination with an operators telephone, an annunciator, acalling-generator grounded on one side, a switching device containingtwo contacts connected respectively to the two sides of said metalliccircuit, two contacts connected to the two sides respectively of saidtelephone, two contacts connected to the two sides respectively of saidannunciator, two contacts one of which is connected with said metalliccircuit and the other of which is connected with the other side of saidgenerator, and a commutator-piece adapted to be placed at will in threepositions, in the first position said two first-mentioned contacts beingclosed to said two second-mention ed contacts, in the second positionsaid tWo fourth-mentioned contacts being closed to each other and in thethird position said "two first-mentioned contacts being closed to saidtwo third-mention ed contacts, substantially as set forth.

14. I11 a telephone-exchange system, two metallic-circuit linestemporarily connected together in metallic circuit for conversation, incombination with an operators telephone, an annunciator, acalling-generator grounded on one side, a switching device containingtwo contacts connected respectively to the two sides of said metalliccircuit, two contacts connected to the two sides respectively of saidtelephone, two contacts connected to the two sides respectively of saidannunciator, two contacts one ofwhich is connected with said metalliccircuit, and the other of which is connected with the other side of saidgenerator, a commutator-piece adapted to be placed at will in threepositions, in the first position said two first-mentioned contacts beingclosed to said two second-mentioned contacts, in the second positionsaid two fourth-mentioned contacts being closed to each other, and inthe third position said two first-mentioned contacts being closed tosaid two third-mentioned contacts, and a key in circuit with saidgenerator, having a pair of contacts normally closed but opened at thewill of the operator substantially as set forth.

15. In a telephone-exchange system, a pair of loop-switch plugs the twocontact-pieces of each of which are respectively connected with the twocontact-pieces of the other by flexible switch-conductors, incombination with an operators telephone, an annunciator, acalling-generator grounded on one side, a switching device containingtwo contacts connected respectively to the two flexibleswitch-conductors, two contacts connected to the two sides respectivelyof said telephone, two contacts connected to the two sides respectivelyof said annunciator, two contacts, one of which is connected with one ofsaid conductors, and the other of which is connected with the other sideof said generator, and a commutator-piece adapted to be placed at willin three positions, in the first position said two first-mentionedcontacts being closed to said two second-mentioned contacts, in thesecond position said two fourth-mentioned contacts being closed to eachother and in the third position said two first-mentioned contacts beingclosed to said two third-mentioned contacts, substantially as set forth.

16. In a telephone-exchange system, a pair of loop-switch plugs the twocontact-pieces of each of which are respectively connected with the twocontact-pieces of the other by flexible switch-conductors, incombination with an operators telephone, an annunciator, acallinggenerator grounded 011 one side, a switching device containingtwo contacts connected respectively to the two flexibleswitch-conductors, two contacts connected to the two sides respectivelyof said telephone, two contacts connected to the two sides respectivelyof said annunciator, two contacts one of which is connected with one ofsaid conductors and the other of which is connected with the other sideof said generator, a commutator-piece adapted to be placed at will inthree positions, in the first position said two first-mentioned contactsbeing closed to said two second-mentioned contacts, in the secondposition, said two fourth-mentioned contacts being closed to each other,and in the third position said two first-mentioned contacts being closedto said two third-mentioned contacts, and a key in circuit with saidgenerator, having a pair of contacts normally closed but opened at thewill of the operator, substantially as set forth.

In witness whereof I hereunto subscribe my name this 23d day of June,1890.

MILO G. KELLOGG. Witnesses:

EMIL ABENHEIM, C. STRIOH-OHAPELL.

